Irrigation pipes are generally known and are described for example in documents: EP865541, EP278049, U.S. Pat. No. 5,688,072, U.S. Pat. No. 6,543,509.
The prior art documents show at least two types of pipes. In one case, the pipe is manufactured by folding a longitudinal tape and by securing the longitudinal edges. The latter are overlapped by a certain extent and dripping units are made, providing ribs according to a predetermined pattern and in one of the marginal, longitudinal bands of the tape. When the marginal bands are overlapped for creating the pipe wall, ribs make passages and/or chambers composing individual dripping units by being interposed between said marginal bands and by keeping them spaced apart.
In this case, the pipe is not closed, and moreover the tape forming one of the two walls of dripping units is not present.
Other prior art documents mentioned above, on the contrary provide for the dripping units differently. In these pipes, a tape intended to form the sequence of dripping units together with the inner side of the pipe is inserted and chemically-physically adhered to the inner wall of the pipe, whereas the pipe is made by a tubular wall that is already closed in its section. The invention relates particularly to this type of pipes with a previously closed or continuous cross section, wherein the sequence of dripping units is not provided along the band that by overlapping and/or a chemical/physical adhesion mutually connects the two marginal, longitudinal bands of a tape folded about an axis parallel to the longitudinal axis of the material tape and/or the finished pipe.
Concerning the operation of these pipes, there are contrasting needs and conditions. On the one hand, the distribution of the delivered fluid throughout the length of the pipe under different conditions of pressure of the fluid is desired. On the other hand, there are also needs for avoiding too small passages and chambers, which can be easily clogged due to minute impurity particles present in the fluid.
To this aim, the inlet element of dripping units includes a filter. However, such filter has to be selective enough to prevent relatively small impurity particles from entering. That causes the flow rate of each dripping unit to considerably decrease and so a control of the fluid pressure should be required, in order to increase it to predetermined higher values.
Moreover in known pipes it has been highlighted above all with low fluid pressures and particularly for long lengths of the irrigation pipe, that there is a lack in evenness of the delivery flow rate of the fluid from delivery holes arranged throughout the pipe length, particularly the condition according to which a greater fluid amount is delivered from some delivery holes than other ones.
More generally, the invention aims at providing a pipe of the type described hereinbefore, wherein the sequence of dripping units is made such that a better evenness of the fluid flow delivered from holes of the sequence of delivery holes is guaranteed and also for great lengths of the irrigation pipe and/or for low delivery pressures.
In addition, the present invention is directed to guaranteeing that even if an inlet filter and/or passages of fluid inside the structure of some dripping units are clogged, the fluid delivery is not completely stopped from delivery hole or holes served by dripping units subjected to said malfunctioning conditions.
Therefore, the invention aims at obtaining a greater delivery evenness and a greater certainty about the operating life and safety of the delivery pipe.
All that without greater manufacturing and maintenance costs.
The present invention aims also at improving a pipe of the described type, such that by means of simple and cheap expedients, it is possible to effectively filter the fluid before it enters in dripping units, without restricting the flow rate of the entering fluid, but potentially increasing it with respect to known dripping units of this kind of pipe.
Particularly as regards this specific aspect, the invention aims at improving an irrigation pipe of the type described hereinbefore by providing a new pattern of projections or ribs projecting from the tape forming one of the constructive parts of the sequence of dripping units, by which a new type of element filtering the fluid is obtained at the inlet side of the dripping units.
A further aim of the invention is to provide an effective filtering action and at the same time a satisfying supply of the flow rate of the fluid to be delivered to dripping units even when the filtering element is partially clogged.